Mariah Carey debuted her bikini body on the May cover of Shape magazine, after losing 30 pounds in six months on the Jenny Craig weight loss program.

The 42-year-old singer posed on the cover in a bikini bottom and off-the-shoulder striped crop top (pictured above opposite a August 2010 photo of the singer). Carey was named Jenny Craig's latest Brand Ambassador and started their program in late July, three months after giving birth to twins.

Carey, whose height spans 5-foot-9-inches told the magazine that she thought she would never recover her body after gaining 70 pounds during her pregnancy.

"I put on around 70 pounds," Carey told Shape. "But if you look at photos of me when I was pregnant, you'd say, 'Wow, she gained 9,000 pounds!' A lot of it was water weight because I pretty much had head-to-toe edema, which is very painful."

"Luckily, all the swelling went away fairly quickly after the babies were born," Carey continued. "Then I had about 30 more pounds to drop. I have such empathy for people who need to lose a lot of weight, because I know what they're going through. I remember thinking at the time, 'I'll never look or feel the same again.'"

Carey credited Jenny Craig's structured eating plan for her success and told the fitness magazine that her metabolism has changed since giving birth.

"I used to be able to slim down just by exercising more, but that's changed. Since having the babies, I realize that 90 percent of losing weight is my diet."

Carey and husband Nick Cannon, 31, welcomed son and daughter Moroccan and Monroe in April. She married Cannon on that date three years beforehand.